Roller shades or roller blinds are common forms of window coverings used in both residential and commercial applications. Most roller shades or blinds utilize a roller tube that is retained within a frame or housing, generally referred to as a “cassette”, where the roller has wound thereon one end of a fabric while the other end of the fabric is fixed or secured to the cassette. A bottom bar is attached or otherwise secured to or over the fabric to act as a weight to hold the fabric relatively taught, and to provide a pleasing visual appearance to the bottom portion of the fabric. As the fabric is wound or unwound about the exterior surface of the roller tube the amount of exposed fabric below the cassette is altered thereby allowing more or less of a window about which the blind or shade is mounted to be exposed. Typically, the bottom bar would be permitted to slide along the fabric as it is wound or unwound over the roller tube so that the bottom bar is at all times positioned at the lower-most point of the fabric that extends outwardly from the bottom of the cassette.
Others have appreciated that when winding the fabric onto the exterior surface of the roller tube (and effectively “opening” the blind or shade), eventually the bottom bar will be raised upwardly until it reaches a point of contact with the cassette. Doing so can often have the undesirable effect of pinching the fabric between the bottom bar and a portion or portions of the cassette, which in some instances can result in damage to the fabric, or in other instances result in a creasing or pleating of the fabric, both of which can diminish the appearance of the blind. In order to prevent the bottom bar from contacting the cassette and to help prevent any resulting damage, pleating or creasing of the blind fabric, where the roller tube is activated through the movement of a chain it has been proposed to incorporate a chain stop that prohibits the chain from being moved beyond a predetermined position. In that manner the roller tube is prevented from being wound to the point where the bottom bar contacts the cassette. Others have also suggested that installers screw, bolt or otherwise clamp separate and discrete bottom bar stops onto the rear face of the cassette during installation of the blind or shade, where such stops limit the upward movement of the bottom bar. While both of these methods have met with limited success, each requires manufacturers to produce separate independent components, requires installers to expend time and effort to install chain stops or bottom bar stops, and each also suffers from the potential of the stops being later removed or falling off, leaving the bottom bar open to being lifted to the point where it pinches the fabric against the cassette. It will also be appreciated that in instances where the roller tube is operated by an electric motor, or by a clutch that is activated by a cord or cable, the utilization of a traditional chain stop will be ineffective.